1. Field of the Invention
This invention relates to a novel resolving agent. More particularly it relates to a packing for liquid chromatography with which a racemic mixture can be optically resolved. The resolving agent proposed by the present invention comprises silica gel as a support, a spacer moiety which introduced by reacting a silane treating agent with said support and a metallic salt of optically active D- or L-tryptophane, or D- or L-tert.-Leucine, chemically bonded to said spacer.
2. Statement of Prior Arts
Conventional packings for optical resolution wherein optically active proline or hydroxyproline is bonded to silica gel include those reported by G. Gubitz et al. (cf. J. High Resolut. Chromatogr. and Chromatogr. Comm., 2, 145 (1979)), K. Sugden et al. (cf. J. Chromatogr., 192, 228 (1980)) and V. A. Davankov et al. (Angew, Chem. and Ed. Engl., 21, 930 (1982)). Each packing as described above has a carboxyl group bonded to a copper ion via a coordinate or ionic bond and resolves a racemic mixture by taking advantage of the difference in the free energy of interaction between enantiomers of a racemic amino acid capable of coordinating with said carboxyl group.
However optically active groups which are known as available in these packings for optical resolution are limited in number, i.e. 2-azetidinecarboxylic acid, proline, hydroxyproline, allohydroxyproline, valine, histidine, cysteinic acid, aspartic acid, serine, threonine, tyrosine, alanine and isoleucine.
We have studied to further improve the properties of these conventional packings for optical resolution and consequently achieved the present invention.
That is, each of known optically active groups is effective in resolving only limited amino acids so that it is very difficult to optically resolve some amino acids therewith.